Energy storage devices (ESDs), such as batteries, are commonly implemented in vehicles to provide electrical power to power various electrical loads. The ESD is discharged as it powers a load. In certain ESDs, lead-acid batteries in particular, sulphates form on the internal components of the ESD. The sulphates decrease the surface area available to the electrolyte and increase internal resistance. More sulphates appear on the internal components with each subsequent discharge cycle.
To reduce the presence of sulphates in the ESD, the sulphation process is reversed during a refresh recharge. For example, lead sulphate (PbSO4) on the ESD components can be removed through sustained charging of the ESD at a higher than normal voltage. In most battery chemistries, the refresh recharge doubles as an equalization charge that corrects for voltage and individual energy variations of the modules in a string of batteries. In a hybrid vehicle that employs an engine ON/OFF strategy, refresh recharge can be difficult to implement. More specifically, the refresh recharge may require the engine to run for an extended period. Regenerative braking may also need to be disabled.